Type I collagen is the principal form of collagen in bone. Breakdown of type I collagen includes the cross-linked carboxyterminal telopeptide region. Measurement of this in serum or urine correlates with degradation of type I collagen, which in turn reflects osteoclastic activity. In multiple myeloma increased levels of the cross-linked carboxyterminal telopeptide region of type I collagen (ICTP) are seen with osteolytic activity during disease progression, while levels in the reference range are seen in those responding to therapy or with stable disease. Levels of telopeptide correlate with the number of bone lesions and can serve as a predictor of patient survival.
